Collect the Pieces
by ForcePassioneAndKibou
Summary: One day I imagined what if post-pacifist run you could put Gaster back together. It'd take an entire crew, and a time traveling space ship to do that. Maybe on the surface they had the right resources to make it happen. This fic deals with three alternate endings to what if Frisk and company managed to collect all the pieces.
1. Linear A

Post-Pacifist

* * *

The space ship slowed and gently set itself down on a rocky outcropping of Mt. Ebott. Frisk and Sans exited the ship walking over to the cave entrance. As it turned out, there were many caves in Mt. Ebott, but there were only two leading to the true Underground which the monsters had left three years earlier.

"so, this is the last place. to be honest, kid, i didn't expect this day to ever come. or any of this to happen, really," Sans said as they both stood there. Frisk remained quiet allowing the skeleton to speak his mind. Through their years spent together, they knew he always appeared to carry a heavy load on his mind.

"i'm a little worried about going in there. i mean, being split into dozens of pieces and being suddenly put back together. what would you do?"

"…"

"you're right, kid. we won't know anything until we go in there. don't be afraid. i'm right behind ya," assured Sans giving Frisk a complementary wink. They shifted the backpack they were carrying on their back and walked inside the cave known as Cave of Echoes.

It wasn't dark at first, but quickly the light of day and the hum of the space ship disappeared. Frisk couldn't hear Sans' footsteps, but they knew he was following. He preferred to be kind of secretive about it was all.

The cave began to have a familiar blue glow when Frisk rounded a corner. They saw the path extended into a cavern covered in echo flowers kept alive by a pool of water. The flowers repeated the sound of their footsteps. This beautiful, nostalgic sight became cut short by a sudden bright flash of light.

At the end of the small cavern a grey door appeared fixed to the wall. Frisk walked over and turned the knob their determination too strong for any sense of caution. They found the room inside a stark white and empty except for a formless black orb.

Frisk took off the backpack taking out of it a similar, but bigger, black orb. It began to levitate and floated over to the other orb fusing together. Another bright flash followed causing Frisk to wince.

They saw standing in the center of the room a skeleton dressed in black. He had Papyrus's slender and tall stature, but the smile on his face closely resembled Sans' own. As he looked around with drooping eyesockets little black specks fell off of his frame. He caught sight of Frisk and the smile dimmed.

" **ah, so you are the one who…put me back together…** " Gaster's voice sounded harsh and rusted from disuse. He attempted to clear his throat and speak more clearly, but it didn't helped much. " **Then I apologize, human, for what I am about to do. It was nice meeting you.** "

Suddenly, Frisk was pulled into a fight.

" **But you cannot be allowed to exist.** "

Frisk watched as Gaster's eyes swam with blue and orange magic. From behind him large circular voids opened and huge, unfamiliar skulls appeared out of them humming with energy. Frisk dodged the blasts of magic they fired at them. Next there came a barrage of bones, and they barely managed to get all the movement combinations correct.

" **Hm. You see, human, I have seen all the harm you could have done. All the resets you could ever make. All the routes you could take.** "

Frisk used that moment of dialogue to catch their breath before another barrage of bones. These were more fierce than the ones they encountered long ago with Papyrus. Frisk could see the skulls hovering close by Gaster's side waiting to be used very soon.

" **Letting you live would put everyone at risk. If I know the truth, why let you be if I have the power to take your soul?** "

As Frisk predicted, the skulls came at them firing no longer solitary blasts but short, strategically angled ones. They decided to act, to plead their case to Gaster because Frisk knew of their power to reset. They remembered taking an oath not to use it ever again.

" **Hmpf. Your words are empty to me, human. I see you only as a threat.** "

Gaster's eyes changed to purple, and Frisk felt a familiar tug on their heart. It was as if it had been strung up by an invisible thread. Gaster spoke again after they managed to survive the attack mostly unscathed,

" **Spider magic is rather easy to learn once you've seen it a few hundred times. Can your resilience last?** "

Frisk dealt with not only the spider magic, but another bone assault ending up bruised in the process. They could feel Gaster's resolve to kill them and keep this timeline safe. It distinctly reminded them of those fights from years ago.

Frisk had to take action again. This time they called for help.

" **You were followed? Of course you wouldn't be able to find all traces of me without help. How silly of me.** "

The door to the room became devoured by a circular black void. Frisk felt a sense of dread travel through their body down to their very soul. Gaster had so much power, how would they win without the others?

Frisk took a deep breath. The others would find them. Even if their determination served as the only spark of light in the void Gaster might throw them into, they would be found again.

" **The look on your face… That is your determination? In person it does suit you well. Now perish.** "

Frisk felt the thread disappear from their heart and be replaced with a heavy weight. Bones and blasts were thrown their way, not haphazardly, but with surgical precision. At the end of the bout, Frisk was panting and heavily bruised. The weight on their heart seemed to grow heavier as they realized what might have to be done. Something they remembered resorting to only once before.

Gaster raised a skeletal hand when suddenly Frisk was tugged backwards. The void blocking the door broke like glass, and the grey room opened up into the cavern of echo flowers.

The sound of shattering glass echoed around them briefly before a voice silenced them.

" _ **Sans.**_ "

"well, this wasn't the reunion i was promised," said Sans dispelling his magic. Frisk stood in front of him and saw on either side Undyne and Toriel. Both of them looked prepare to fight.

"We're here for you Frisk, just like we promised we always would be!" Exclaimed Undyne a spear already in her hands.

"Come here my child. I will heal your wounds," spoke Toriel summoning her healing magic in her hands. She proceeded to guide Frisk out of Sans' way.

"[Sans, my son, what are you doing?]" Gaster spoke in a language Frisk didn't recognize. His face became clouded with disappointment as he locked eyes with the smaller skeleton. They could see magic still danced in his gaze. It wasn't dreadful to look at with the others there.

"it's been a while since i talked like that. you might have to repeat yourself," Sans paused as Gaster looked ready to do just that when he broke in with, "just kidding, i heard you the first time."

" **Sans, you know what they're capable of doing.** "

"yeah, you think i didn't know? i practically lived with that for years. i also wasted a lot of time sitting around trying to work on the machine you left me. all those times i had dreams about you. how could i forget all that?" Sans paused again to collect himself. "the reason i went through all this trouble to bring you back was because of Frisk. living with them, and talking with them, i realized the only thing missing when i got here to the surface was you."

"so dad. please. stop with the fighting and come home," Sans pleaded holding out a hand. Gaster stared at him as the echo flowers whispered the last words. _Come home… Come home…_

Gaster looked from Sans' face over to Frisk who was mostly recovered and standing on their own. He looked back at Sans and heaved a sigh. The floating skulls disappeared back into their respective black voids. The magic disappeared from his eyes. The smile appearing on his face conveyed how tired he looked.

"It's been so long since I heard you ask me to come home." Gaster spoke in a gentle tone the rusty quality gone for the time being. He walked over and clasped Sans' hand with both of his own.

"yeah…too long you could say," Sans replied looking up at his father with his usual smile. They remained like that for a few seconds before Gaster pulled his hands away to look at the others.

"Where are my manners? Allow me to introduce myself. I am W.D. Gaster the former Royal Scientist for the kingdom of monsters." He looked down at Frisk the smile gentle now. "I thank you for being such good friends with my sons."

Toriel did a polite sounding _ahem_ and, after catching her eye, Gaster continued with, "And I apologize for my outburst of anger."

Frisk returned the smile and said it was okay. They understood why Gaster would go out of his way to do such a thing. So many monsters had done the same.

Undyne pointed out they should probably get back to the ship since Papyrus and Alphys might be worried about them taking too long.


	2. Linear B

Post-Pacifist but Genocide was done before

* * *

Chara exited the space ship as soon as it landed on the rocky outcropping of Mt. Ebott. Upon locating the last piece of Gaster, they had systematically taken out every monster on board. It was easier since some of them had begun to go "mysteriously missing" beforehand. Fighting Sans, however, wasn't easy even if this counted as the unofficial second fight between them.

Chara looked with cold eyes at the cave entrance. Putting Gaster back together had been a strange idea to go along with. Maybe destroying this monster once and for all would grant them a power so great the obliteration of existence would become permanent. Spending a long time in the void a monster _had_ to become prowerful from it, right?

Chara walked forwards into the Cave of Echoes ignoring how dark it became. When the blue bioluminescence came into view, they remembered being in the Underground three years before. Letting Frisk have control was fun to watch. Seeing them befriend everyone again, and then forcing them to kill their friends later on the surface. What a joyous occasion it had been.

Chara's nostalgia became cut short by a bright flash of light. A grey door appeared at the end of the cavern full of echo flowers. They approached and opened it to a grey room where a black orb floated in its center. Taking out the piece of Gaster from their backpack and they watched the two join together.

Chara saw standing in the center of the room a skeleton dressed in black. He had Papyrus's slender and tall stature, but the smile on his face closely resembled Sans' own. Gaster looked around with drooping eyesockets little black specks falling off of his frame. When he caught sight of Chara he frowned deeply.

" **you are the one who made me whole?** " His voice sounded harsh from years of disuse. " **I recognize the look in your eyes for I have seen it too many times.** ** _Chara_** **.** "

They were pulled into the fight willingly.

" **You cannot be allowed to exist.** "

As Chara expected of the skeleton they were assaulted with blue and orange magic laced bones. The skulls appearing out from behind Gaster were familiar having seen them used before by Sans. Chara expertly dodged the attacks and took a swipe with their knife.

Gaster managed to dodge.

" **I know your sins. You must have played nice to collect all pieces of me.** "

Chara made it through another barrage of bones. They took another swipe, but Gaster managed to evade again. At least this skeleton was trying to be more clever than Papyrus.

" **That also means my sons are dead because of you.** "

Chara noticed Gaster's eyes change from orange and blue to purple. An unfamiliar sensation pierced their heart as it felt like it was being tugged on by a string. Getting used to the attacks this turn proved difficult.

" **Spider magic is your weakness? I suppose this time the human didn't fight Miss Muffet.** "

Chara gritted their teeth in frustration for a few seconds. Then, they began to smile as they brandished their knife. This fight is exactly what they needed to let this world go out with a big bang.

Gaster noticed the smile and had his Blasters keep Chara busy. He switched between the skulls and spider magic a few times to try and shake off the child's grin. Their determination was too strong to wipe away easily. He resorted to closing off the exit to the room with a black void.

" **…I see now that I might be killed here. This is a room where my consciousness has spent countless hours desiring to be set free.** "

Gaster gestured with his hands and more of the room became devoured by the black void.

" **Without my sons, my past friends, what good is getting out of here?** "

Chara noticed the void underneath them and decided to test it with their knife. It felt dense like metal.

" **Being trapped for eternity with you sounds pleasant compared to being free. Keeping this timeline safe is just a bonus.** "

The entire room became a void. Chara stared at Gaster as the skeleton stared back. He knew this game. If Gaster and Sans were really related-

" **You cannot wait me out like my son. I am used to an eternity of waiting. Go ahead and test my patience.** "

Chara obliged with a swing of their knife. Gaster fluidly dodged to one side.

" **Your determination is futile. Chara, you cannot work a miracle here with it. I control this domain and here we shall stay.** "

Chara narrowed their eyes and turned their attention to the floor again. They then turned around to face where the door had been. Walking over to it, Chara began to stab at where its hinges should be.

Gaster watched them stand there and stab at nothing. He crossed his arms knowing even if Chara thought they could carve out the door, the door itself was already gone. It was a concept so simple he didn't feel the need to spell it out.

After a while of pecking at nothing, Chara decided to stop. They felt the place they had been stabbing at and noticed no marks had been left. The void couldn't be penetrated from the inside.

Chara, taking stock of the situation, looked over their shoulder at Gaster. This monster had control over the room's properties. His magic dealt with more than just manipulating souls- he could manipulate space. There had to be a limit to it. It happened with Sans, and it happened to every monster.

" **I see determination has yet to leave your cold eyes. You will find no limit to break here.** "

Chara pocketed their knife and dusted off their hands. Gaster took immediate notice and frowned. He did not move to take action.

Next, Chara sat on the floor pulling out of his pockets dusty weapons they had kept from this past year. Never knew when a monster needed a more efficient way to be killed.

" **Your insult adds no injury, Chara.** "

They cleaned off the weapons one by one. Gaster felt himself losing his patience watching the dust scatter. Chara's actions were intentional, they wanted him to lose to anger.

After the sixth weapon, Gaster finally decided to let loose with his rage built up upon years of watching countless monsters slain by this small creature.

" _ **I will strike you down!**_ "

The void rumbled around them. Magic blazed in the skeleton's eyes as the very confines of space seemed to writhe around the room. Chara stood up summoning every ounce of cold blooded determination they had inside themselves. The room eventually imploded taking them both to places unimagined.

In the darkness, there appeared a light. Another light appeared and took the smaller light with it. Together, they travelled out of the dark and onto Mt. Ebott.


	3. Schism

Post-Pacifist with Max Friendship with Papyrus

* * *

" **Spider magic is rather easy to learn once you've seen it a few hundred times. Can your resilience last?** "

Frisk dealt with not only the spider magic, but another bone assault ending up bruised in the process. They could feel Gaster's resolve to kill them and keep this timeline safe. It distinctly reminded them of those fights from years ago.

Frisk had to take action again. Seeing as Gaster wouldn't listen to their pleading, this time they called for help.

" **You may call for help but I will keep you here, far away from where you can harm them.** "

Gaster raised his hand, and the door to the grey room became devoured by a black void. Frisk began to feel helpless seeing the exit lost. They took a deep breath and summoned their determination. Hope swelled inside their chest nourished by the fond memories they had made with their family on this journey to collect the pieces of Gaster.

" **The look on your face… That is your determination? In person it suits you well. It…reminds me of something…** "

Frisk watched as Gaster became distracted by a memory. The thread holding their soul vanished as he lost concentration. Then, Frisk felt themselves tugged backwards. The sound of the void shattering reverberated around them, mostly due to the echo flowers.

"THIS WASN'T EXACTLY THE REUNION I WAS PROMISED," said Papyrus dispelling his magic. The tall skeleton stood beside his smaller brother. On either side they were flanked by Toriel and Undyne. Toriel walked around and escourted Frisk to one side so they could be healed from their fight.

Gaster jerked out of his daze to focus on the situation.

" **Papyrus…** Sans…" His voice adopted a gentle quality becoming a drastic change from its earlier harsh tone. Sans looked over at his brother who had become silent.

"go ahead, bro. let 'im have it," he encouraged with a wink. Papyrus stepped forwards acting more shy than usual.

"DAD…IT'S BEEN A LONG TIME. I'D REALLY LIKE TO CATCH UP WITH YOU, AND TELL YOU ABOUT EVERYTHING I'VE BEEN DOING. BUT FIRST! YOU NEED TO STOP FIGHTING MY FRIEND FRISK!" Papyrus gained courage the more he spoke. He gestured over to Frisk who stood off to one side. "WITHOUT FRISK WE MIGHT NOT HAVE FOUND YOU! AND I NEVER WOULD HAVE GOTTEN THE CHANCE TO EVER SEE YOU AGAIN. DAD!"

Gaster watched as Papyrus approached him holding out his hands.

"I'M SURE SANS FEELS THE SAME WAY I DO ABOUT THEM! PLEASE, STOP FIGHTING!"

Gaster looked from Papyrus, to Sans, to Frisk, then back to Papyrus. Judging by the expression on his face, it looked as if he were trying to hold back tears. He reached forwards and held hands with Papyrus.

Silently, Papyrus noticed on the back of his father's hands there were circular scars. In fact, there was a scar on the right side of his father's skull as well.

"Hearing you call me dad again sounds sweeter than I anticipated," Gaster said finally with a small smile. Papyrus appeared to light up as he interpreted the answer as a yes.

"OH, WOWIE! I'M! SO HAPPY TO HEAR THAT!"

"you're crying, aren't you?"

"SANS! YOU CAN'T EVEN SEE MY FACE!"

"i don't need to see it," Sans paused as he walked forwards coming to stand beside Papyrus. "dad, let's save this family stuff for when we're out of here, okay? trying to hear you two over the echo flowers repeating Papyrus is hard."

Gaster's smile widened a little, and he allowed himself to be lead by Papyrus towards the exit. Sans followed them choosing to let his brother take most of the attention.

"Papyrus wait! What about Frisk?" Undyne called attention to them as they stood beside Toriel. "Shouldn't Gaster…y'know…"

"OH, RIGHT! YOU SHOULD PROBABLY APOLOGIZE FOR TRYING TO KILL FRISK. NOT THAT YOU'RE ALONE IN THAT BOAT."

"Yeah! That boat is full and rockin'!" Chimed in Undyne with a laugh. Gaster let go of his son's hand and walked over to Frisk. Glancing at Toriel he looked down and said,

"I apologize for my outburst of anger, Frisk. Allow me to introduce myself. I am W.D. Gaster the former Royal Scientist. From the bottom of my soul, I thank you for being such good friends with my sons."

Frisk smiled up at Gaster and accepted the apology. The skeleton smiled back and walked with his sons out of the cavern. Undyne closely followed behind them pestering Papyrus with questions about his father. Their conversation was quickly lost.

Toriel affectionately patted Frisk's head. It remained an old habit she had yet to break.

"Well done my child. I believe you've managed to bring their family much closer together," she praised. Frisk kept the smile on their face as they walked with Toriel out of the cavern. The echo flowers repeated in their wake: _closer together, closer together_.


End file.
